There are just a few days left to apply to NASA's astronaut program, which could eventually lead to a trip to Mars in the 2030s. Mars One and SpaceX hope to be sending civilians even sooner. But before signing up, it only seems fair to make sure all aspiring interplanetary explorers know the risks involved.

So, consider this a bit of a Red Planet reality check, courtesy of Pascal Lee, a planetary scientist at the SETI Institute. Lee spoke at the New Worlds conference 2015 in Austin, Texas, on the topic of settling Mars.

First, let's forget about all the space travel challenges involved in getting from Earth to Mars for right now.

Forget the fact that we're talking about a journey that involves escaping our planet's gravity well and then cruising through space for six months, many times longer than the trip to the moon, which is the farthest from home any human has traveled so far. Scott Kelly has already been in space aboard the International Space Station for nearly a full year now, so at least we know that's doable, albeit with resupply missions less than an hour away regularly launching from Kazakhstan and Florida.

Also forget that landing on Mars will be tricky. We've landed little car-size rovers there, so it's obviously possible, though we'll need to delicately land much more than one little robot to support a manned mission.

Forget all those engineering problems for now, and let's focus on Lee's list of Mars' good and bad attributes as a potential human settlement. On the good side is the presence of water! A key building block to life is already there. It's frozen at the poles and has been seen running just below the surface in salty brine form in warmer regions.

Actually, that's about it for the good news. Prepare your sad-face emojis, because the bad side of the list is five times longer.

Mars One's take on a settlement.

Mars One

Let's start with all the "zapping radiation," as Lee calls it, coming from solar and cosmic rays. Most of the Martian atmosphere was lost to space eons ago, leaving little protection against the intense amount of radiation coming from space and the sun.

For astronauts on Mars to be shielded from all that radiation, they would need to live underground, according to another New Worlds conference talk, by former NASA physician and long-distance biomedical expert Jim Logan. They'd need to put almost 9 feet of Martian soil between themselves and the elements. (It could help to be from a certain city in Iran, as well.)

"There's just too much radiation to be hanging out on Mars in spacesuits or rovers," Logan said.

Adding insult to injury, what little atmosphere Mars does have is basically toxic to humans because of its high carbon dioxide content. This is not an insurmountable obstacle, of course. Plants would be happy to suck up that CO2 and convert it to oxygen, among other possible solutions. Still, it does greatly add the constant threat of suffocation to astronauts' list of things to worry about.

Speaking of breathing, choking on Martian dust could be another dreadful reality of life there. "It is unknown how the fine Mars dust might affect humans, should they be exposed to it," reads the Mars One website.

To be more specific, according to NASA, it's more the dust than the dust storms that would be the real threat to a settlement, contrary to what you may have seen or read in "The Martian." Martian storm winds top out at 60 miles per hour, not enough to cause much damage, but the dust is much finer than what we have on Earth, surely making it the bane of existence for any moving parts, solar panels and lungs unfortunate enough to be exposed to the stuff.

Should the heating break down on Mars, you could be in a lot of trouble, with temperatures that swing between about 80 degrees F (27 C) to -225 degrees F (-143 C). It's not exactly the place to be caught out in the cold.

Finally, there's the fact that the atmospheric pressure on Mars is extremely low. So low that if you were to walk around without a pressurized suit or rover on the surface, all the water in your body would begin to evaporate. This wouldn't kill you right away, but it would probably make your demise from suffocation even more horrible.

People in the business often like to say that "space is hard," and it certainly is very hard just to escape from the iron grasp of Earth's gravity, holding us tight like an overprotective parent who knows better. But Mars is even harder. Mars wants to kill you and just about everything else.

If, even after this rather harsh reality check, you think that's you, then I salute you. You've still got two days to apply to join the next generation of astronauts who will pave the way to that horribly dangerous but certainly amazing place called Mars.